M-Stage was a very good match with my K702 , and opamp rolling is a great thing , @ tdockweiler and chicolom , i think you will really enjoy M-stage with your Q701 , m-stage as 4 gain settings wich help a lot too . i Compared it to a LD MK3 wich sounded bad with my K702 ... highs totally rolled off , bass not well controled , and seams a lack of clarity in comparaison to m-stage , and too much warmth ... On my M-Stage i tryed 2*OPA627BP (guenines one from farnell expensive but ...) thy are far better than Stock OPA in every aspects , peraphs a bit laid back but with Class A biasing mod (tryed it some months later , it become beter for me , more forward , less dark , clarity seams better , tryed too AD797 very mids centric , more soundstage than OPA627 and even more clarity . But my favorite one with K702 was OPA MOON from audio gd after some weeks they was and are really the best one i heard with my M-Stage + K702 , a great soundstage a bit more warm than the other but still ok , more bodied than other too , and great with details and instruments layering , but it's just my opinion . Actually using a Audio GD C2.1 wich is even better than M-stage , ACSS mode with NFB-2 work wonderfully , and i still can do opa rolling on RCA mode (currently using OPa moons too , really like this ones , but i mostly use ACSS , RCA and opa moons time to time when i went something a bit different from ACSS) . Despite audio GD opas are less on the hype now i still think they are good ones .